<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>wacth</title>

</head>
<body>
<div id="app">
   <input v-model="info">
</div>

<script src="./node_modules/vue/dist/vue.js"></script>
<script>
    var app = new Vue({
        el: "#app",
        data: {
           info:"黑马"
        },
        watch:{
            info(val,oldval){//对info监控
                console.log(val,oldval)

            }
        }

    })
</script>
</body>
</body>
</html>